This invention relates generally to food products, and more particularly to an instant yogurt preparation in dry particulate form which may be reconstituted by admixture with water to provide a product of acceptable texture and flavor and having high nutritional and medicinal value.
Yogurt is a form of fermented milk curdled to a smooth, creamy or custard-like consistency by lactic acid-producing micro-organisms. The production of natural yogurt entails the implant of a beneficial culture of Lactobacillus bulgaricus and sometimes Lactobacillus acidophilus in milk which is then allowed to incubate until these particular species of bacilli establish the proper pH in the milk, after which the milk is chilled to inhibit growth of undesirable microflora.
Because of rising public demand, yogurt is now factory-produced on a large scale and widely sold in supermarkets. But consumers sometimes find it inconvenient to purchase the fresh product or that the product is too costly. However, electrically-heated yogurt makers for do-it-yourselfers are also available so that yogurt can be made at home to suit individual taste. In producing yogurt at home, a yogurt starter in the form of plain yogurt or a commercially-available dried yogurt culture is added to whole or skimmed milk. But whether yogurt is factory-produced or home-made, the processing thereof is time consuming, for it takes many hours of fermentation under proper conditions for the natural yogurt to develop fully. Moreover, both products are highly perishable and require refrigeration for their period of freshness (up to about a week).
When yogurt containing an active culture is consumed, some bacilli pass unharmed through the stomach, for these species favor an acid medium and are therefore not totally destroyed by gastric juices. But when the bacilli find their way into the intestines, they may implant a favorable flora. In any case, whether or not an implant is effected, beneficial vitamins are ingested.
Yogurt is believed to have medicinal value in the control of intestinal fermentation in that it contributes bacteria which establish themselves in the lower intestine and predominate over putrefactive types. Because of this characteristic, yogurt is often prescribed to patients who are required to take large doses of antibiotic drugs. These drugs, as a side effect, act to kill beneficial intestinal bacteria, and it is often necessary, therefore, to replenish such bacteria.
A high quality natural yogurt is one which is low in fat and is starch-free, the yogurt being rich is protein, calcium and other ingredients regarded as beneficial nutrients. Yet while the benefits to be gained from yogurt cultures are recognized, not all brands of yogurt currently on the market include effective amounts of yogurt culture. Indeed, in some brands, mainly those of the premixed or Swiss type, the cultures are often deactivated by the processing.
The texture of a yogurt is also an important factor in determining its acceptability, for yogurt should be free of lumps or curds and exhibit a smooth, custard-like consistency until the set is broken and whey is released. Hence a high quality yogurt is one of good texture which is low in fat, free of starch, and includes effective amounts of active culture as well as protein, calcium and other useful nutrients.
Though some factory-produced yogurt brands currently on the market satisfy all requirements for a high quality product, and it is also possible using home yogurt makers, to provide a high-quality product, it has heretofore not been feasible to produce a satisfactory instant yogurt.
By a satisfactory instant yogurt is meant a dry preparation which can be stored indefinitely and which can be reconstituted simply by adding water and stirring the mixture for less than five minutes to produce a product having a texture, taste and nutritional properties very similar to natural yogurt.
The main value of an instant yogurt as against a natural yogurt resides in its convenience and is based on practical considerations. There are many situations in which a consumer does not have ready access to a supermarket, dairy, or other facility carrying natural yogurt. While the consumer can, if necessary, make yogurt at home, this is a time-consuming operation requiring some degree of skill and also dictating the use of refrigerator to chill and store the yogurt. But even when refrigerated, natural yogurt has a limited life. One cannot safely stock a refrigerator with a large supply of natural yogurt, for in about a week the entire supply might no longer be edible.
With a view to providing an instant yogurt which requires no refrigeration and has a long shelf life, the Ferguson, U.S. Pat. No. 3,080,236 discloses a preparation comprising a dried yogurt powder and a water-soluble dried milk as well as an edible fat and a water-soluble dried starch. Ferguson produces yogurt by adding water to this preparation and stirring. To produce the yogurt powder, Ferguson first makes natural yogurt by implanting a pure culture in milk and after incubation for 12 hours, the resultant yogurt is reduced in volume by evaporation, then placed in vacuum driers until all moisture is removed, after which the dried product is pulverized. In producing a powdered yogurt of this type, substantially all the beneficial micro-organisms are destroyed, and Ferguson's instant yogurt therefore is lacking in the full benefits of good quality natural yogurt.
Moreover, in Ferguson, starch is required to impart sufficient body to the final product, and an edible fat is needed to give the product the appearance and taste of yogurt. But from the dietary standpoint, the inclusion of starch and fat in the product is objectionable.